Reference 1

Level I Good quality evidence Systematic review of RCTs with
consistent findings
High quality individual RCT
Level II Limited quality patient
orientated evidence
Systematic review of lower quality
studies or studies with inconsistent
findings
Low quality clinical trial
Cohort studies
Case-control studies
Level III Other Consensus guidelines, extrapolations
from bench research, usual practice,
opinion, disease-oriented evidence
(intermediate or physiologic outcomes
only), or case series

[1] Caldato MCF, Fernandes VT, Kater CE. One-year clinical evaluation of single morning dose prednisolone therapy for 21-Hydroxylase Deficiency. Arq Bras Endocrinol Metab. 2004;48(5):705-712